At a final stage of a nuclear fuel cycle, spent fuel (a radioactive material) contains a highly radioactive material and is cooled in a cooling pit of a nuclear power plant for a predetermined period of time because of the need of thermally cooling the spent fuel after the occurrence of decay heat to the radioactive material. The spent fuel is then stored in a cask that is a container, transported to an intermediate storage facility, a reprocessing plant, or the like by a transport method such as a truck, and stored or processed at the facility or the like. The spent fuel is hereinafter referred to as “spent fuel assemblies”, because the spent fuel is normally stored in the cask that serves as a container in a state of fuel assemblies.
Generally, the cask is configured to include a main body having one end that is open and the other end that is closed, resin that is provided on the outer circumference of this main body and that is a neutron shield, an outer shell provided on the outer circumference of this resin, a basket that is arranged within the main body and that accommodates the spent fuel assemblies, and a primary lid and a secondary lid that are fixed to one end of the main body.
As described above, the cask stores therein the spent fuel assemblies, and therefore it is necessary to keep the cask shielded, subcritical, and hermetically sealed. Therefore, during the transport of casks, the casks are protected with the both ends of each cask covered with a cask cushioning body. Even if the casks are subjected to drop or the like, the shielding, subcritical, and the hermetically sealing performances of the casks are prevented from being degraded.
Conventionally, there is an example of such cask cushioning body disclosed in Patent Literature 1. This conventional cask cushioning body includes a housing having a hollow interior, and a cushioning material (such as wood) with which the interior of the housing is filled, and partitions made of metal plates that independently partition the cushioning material are provided in the interior of the housing. The partitions are provided horizontally to the height direction of the housing.